There exists a class of novel electronic devices that utilize energy transfer between a relatively hot and a relatively cold surface when these surfaces are separated by a sub-micrometer gap. Collectively, this phenomenon is known as “near-field” energy transfer.
One such family of devices is micro-gap thermophotovoltaics (MTPV) wherein a sub-micrometer gap is used between the emitter and the radiation receiver PV cell to achieve enhanced radiative transfer compared to conventional “far-field” (TPV) systems, as above indicated. Another such proposed class of devices utilizes Coulomb Coupling (CC) as described in U.S. Patent Publication 2008-0060694-A1 of Mar. 31, 2008 and of common assignee herewith. CC involves the transfer of electronic states from the hot surface to the cold surface through direct energetic coupling of hot- and cold-side electrons. Both MTPV and CC can be used to generate energy and involve a relatively hot-side emitter and cold-side receiver separated by a gap, and these and related methods will be herein referred to as “near-field” systems.
There are, however, several challenges faced in attaining gap uniformity, caused by bowing or irregular surfaces, or applied external forces when manufacturing such near-field systems, particularly those that are to be capable of generating commercially significant (>1 kW) power levels. First, one must achieve a very small gap (sub-micrometer) and preferably with gap uniformity between the emitter and receiver surfaces. Secondly, this operation must be repeated many times to achieve an integrated system capable of achieving high power levels; the exact number of times depending upon the power level specified, the size of each individual receiver and emitter chip, and the power density and efficiency of the system. In some embodiments, indeed, the emitter and receiver surfaces may be heterogeneously integrated; whereas, in other embodiments, the emitter and receiver may be fabricated by one-chip monolithic integration techniques. In some embodiments, moreover, the formation of the sub-micrometer gap between the emitter and receiver may occur after these components have been fully and/or individually processed. In such embodiment, indeed, resulting bow and surface irregularities of each chip must be accommodated during assembly.
The present invention deals with structures and methods for overcoming these challenges through the use of appropriately compliant membranes, which preferably contain a fluid that applies compensatory pressure to the rear surface of the emitter, receiver, or both, and thereby helps accommodate for any non-uniformity in the gap between the emitter and receiver.
Such membrane usage also reduces the problem of external forces or pressures acting upon the assembled chip structure that can produce non-uniformity in such gap during use of the chip structures.